WHITE PLAINS, N.Y. — Kerry Kennedy testified at her drugged-driving trial Wednesday that she has no memory of swerving into a tractor-trailer on a suburban New York highway and never sensed that she was becoming impaired after accidentally taking a sleeping pill."If I realized I was impaired I would have pulled over," said Kennedy, ex-wife of Gov. Andrew Cuomo and daughter of the late Sen. Robert F. Kennedy.She was arrested in July 2012 after her car hit the truck near her home outside New York City. She kept driving to the next exit, where she was found slumped over the steering wheel and failed sobriety tests.The prosecution argues that even if she took the sleeping pill accidentally, Kennedy violated the law by failing to pull over when it took effect.Taking the stand on the third day of her trial in White Plains, Kennedy said she remembers the first part of her drive that day but has no memory of the interval between when she got on the highway and when she stopped at the exit.She said she was confused when a man knocked on the window of her Lexus and asked if she was all right."He said, 'Have you been in an accident?'" Kennedy said. "And I said, 'No,' because as far as I was concerned I hadn't been in an accident."Kennedy testified earlier Wednesday that she accidentally took a sleeping pill that morning."I thought I was taking Synthroid, my thyroid medication," she said. But because blood tests revealed a small amount of the sleeping drug zolpidem, "I must have taken the sleeping medication by mistake."Kennedy said she has taken the thyroid medication every day since 1991 and takes the sleeping pills to adjust to time changes when she travels.Kennedy, 54, said the sleeping pills were on the kitchen counter, near the thyroid pills, on the morning of the accident because she was planning a trip.Defense lawyer Gerald Lefcourt showed the jury two photographs — one of the two similar pill bottles and one of the two types of pill. Both pills were light-colored and oblong, but one was slightly longer than the other.Prosecutor Doreen Lloyd said during cross-examination that Kennedy "didn't take the time or the care" to check the label on the medication and asked if she would agree that was careless."I would," Kennedy said.And she asked if the pill really "overtook you without warning.""Yes," Kennedy said.Lefcourt asked her about her big-family upbringing. Kennedy said they lived near Washington because, "Daddy was the attorney general.""My mother raised us because my father died when I was 8," she said. "He was killed when he was running for president."She answered several questions about her work as president of the Robert F. Kennedy Center for Justice and Human Rights, but Justice Robert Neary cut them off, saying, "I'm not sure this is the right forum to go into exhaustive detail."Kennedy had mentioned the possibility of a pill mix-up to police at the accident scene. But Lloyd noted that a few days after the accident, she issued a statement saying her doctors believed a seizure, stemming from an early brain injury, caused the accident. A week later, after blood tests revealed the sleeping drug in her blood, she issued another statement saying, "It now appears that my first instinct was correct."Lloyd accused her of switching defenses and using a public relations firm because she was worried "what the public would think about you."Kennedy said she "wanted the truth to be out."Lloyd also mentioned that in 2010, Kennedy refilled a 30-tablet sleeping pill prescription 38 days after getting the original prescription."Do you recall taking zolpidem on an everyday basis?" the prosecutor asked."Absolutely not," Kennedy said. She said she may have lost the first bottle and acknowledged it was a dangerous thing to misplace.